The present invention relates to a working vehicle suitable for a turf grass management working vehicle used for work such as fertilizing, chemical spraying, lawn mowing and the like in golf courses.
In the golf courses and parks, the working vehicle, also called turf grass management working vehicles, are used to grow turf grass. With such vehicles, various types of works such as the fertilizing, spreading topdressing, the spraying chemicals, aerating soil by injecting air, or clearing tree leaves by using a blower are conducted. The various types of works are carried out with an attachment, appropriate for the types of works, mounted on the bed of the working vehicle.
For such working vehicles, maximum travel speeds may be limited by laws and regulations such as restrictions on off-road vehicles in the U.S. With respect to the U.S. restriction, the maximum travel speed of the vehicles is limited to about 38.6 km/h (or 24 mile/h). The restrictions are also applied to the vehicles for the work in the golf course. Consequently, in a conventional working vehicle, a speed limiting device using an electronic control unit for controlling the engine is provided to limit the vehicle speed so that the vehicle does not exceed the legal speed limit.
In this speed limiting device, the vehicle speed is detected with a vehicle speed sensor which detects the number of revolutions of a wheel, and the detected speed is inputted to an electronic control unit (ECU). In the electronic control unit, an upper limit value of the vehicle speed is preset, and when the vehicle speed reaches the upper limit value, the engine speed is controlled so that the engine speed does not increase any more. Thereby, the engine speed is limited and controlled so that the vehicle speed does not exceed a predetermined one.
On the other hand, an operator of the working vehicle is not always a skilled person. In such a case, the vehicle speed is preferably limited to a lower speed than the maximum speed in accordance with the laws and regulations. Also, when a heavy object, such as a container of chemical spraying machine, is mounted on the vehicle, higher safety is achieved with a lower speed limit which is independent of the skill of the operator.
Contrary to this, with the conventional vehicle speed limiting device described above, although the device can limit a maximum speed in accordance with a legal speed limit, changing the speed limit with respect to the operator""s skill or the weight of an object mounted on the vehicle is not taken into account. Therefore, the restrictions are required in that, when the vehicle is operated by a beginner, the person must be accompanied by a skilled operator about the vehicle. Also, the restrictions are required with respect to a limit in the amount of a load which is to be mounted on the vehicle. These restrictions have all caused problems in terms of work efficiency.
An object of the present invention is to provide a working vehicle with which a travel speed limit can be appropriately changed according to a working environment, so that safety and work efficiency can be improved when operating the working vehicle.
The working vehicle according to the present invention is driven by an engine and traveled with a working machine mounted thereon. The working vehicle comprises a vehicle speed sensor for detecting a travel speed of the working vehicle, travel mode changeover means for setting any one of a plurality of travel modes with different predetermined speed limits, and control means for controlling the working vehicle in such a manner that the travel speed of the working vehicle detected by the vehicle speed sensor does not exceed a predetermined speed limit of the travel mode set by the travel mode changeover means.
According to the present invention, because a plurality of vehicle speed limits are provided which can be selected as required, a speed limit can be appropriately changed depending on the operator""s skill and/or the working conditions such as the weight of an object mounted on the vehicle, the weather, and the like. Consequently, a person other than an experienced operator can also safely operate the working vehicle, thereby safety at work can be secured.
Also, in the working vehicle of the present invention, the travel mode setting means may have, for example, two travel speed modes, a high speed travel mode and a low speed travel mode. The high speed travel mode limits the travel speed of the working vehicle at or below a predetermined first speed limit, and the low speed travel mode limits the travel speed at or below a second speed limit which is set at a speed lower than that of the first speed limit. Thereby, each travel speed of the high speed travel mode and the low speed travel mode can be kept at or below each predetermined speed limit thereof, so that the safety at work can be secured.
Furthermore, a switch which is operated by the operator may be provided as the travel mode changeover means, and the operator can select an appropriate travel mode with the switch. Additionally, a switch which is operated by a vehicle supervisor and which cannot be operated by the operator while traveling may be provided. With this switch operational, mistakes by the operator can be prevented and safety can be improved.
Additionally, in the working vehicle of the present invention, weight detecting means for detecting the weight of a working machine mounted on the working vehicle may be further provided and be so arranged that the travel mode changeover means automatically changes the travel mode according to the weight detected by the weight detecting means. Thereby, the travel mode is automatically changed over to the low speed travel mode independently of the operator""s skill when the weight of an object mounted on the vehicle is heavy. In this way, operational mistakes by the operator can be eliminated and safety can be improved.